Freshwater mussel [Unionidae]

Freshwater mollusks found in this area include Curtus' mussel,
Judge Tait's mussel, and the Penitent mussel. These mussels are in the
family Unionidae, a family restricted to North America. A far larger percentage
of this family are imperiled than any other taxonomic (species) group.

Freshwater mussels can live up to 50 years. In the parasitic
larval stage of the mollusk lifecycle it is dependant on fish within its
habitat for nutrients and mobility. However, only a few host fish are
known. Mature mussels bury themselves in the riffles and shoals and feed
by siphoning phytoplankton and other plant matter from the water. Reverse
siphoning is used to expell undigestible particles from the shell. Silt
in the water can kill mussels by clogging their feeding siphons.

Major factors affecting mussel populations are alterations
in temperature, waterflow, and siltation caused by stream damming and
channeling. Agricultural runoffs and industrial practices have also affected
the mussel habitat by degrading water quality and causing siltation. Because
mussels are filter feeders, the effects of pollution are intensified due
to the large quantities of water drawn through their siphons in the feeding
process. Another significant threat to this species is the widespread
and rapid population growth of the introduced zebra mussel. The zebra
mussel not only competes with native species, but also attatches to them,
adding so much weight that the native species cannot open to feed. In
the past, commerial harvests contributed to the decline of freshwater
mussels but this industry has since been reduced.